Am I using GroupSequence correctly? Constraints aren't called when validating this form.

MyFormType.php

<?php

class MyFormType extends AbstractType
{
    public funcion buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('username', 'text', [
                'required' => true,
                'validation_groups' => new GroupSequence(['Default', 'Strict']),
                'constraints' => [
                    new NotBlank(),
                    new Length(['min' => 3]),
                    new Regex(['pattern' => '/^[a-zA-Z][a-zA-Z0-9_-]+$/']),
                    new NotForbiddenUsername([
                        'groups' => ['Strict'],
                    ]),
                    new NotExistUsername([
                        'groups' => ['Strict'],
                    ]),
                ],
            ]);
    }
}

I ran into this issue today with Symfony 2.7.6. Glad that the workaround does work for me. Was the issue already solved?